Process for the preparation of gluconic acid and its lactones



Patented Jan. 9, 1934 UNITED STATES PATENT OFFICE PROCESS FOR THEPREPARATION OF GLUCONIC ACID AND ITS LACTONES No Drawing. ApplicationJune 6, 1932 Serial No. 615,760

17 Claims.

This invention relates to a process for the preparation of gluconic acidand its lactones, and is a continuation in part of our copending application S. N. 523,186, Process for the production of g d-glucono t-lactone,filed March 16, 1931, patented June 7, 1932, No. 1,862,511. 1

When an aqueous gluconic acid solution is concentrated, either bystanding in a desiccator over a drying agent, or by evaporationdn vacuo,or by evaporation at ordinary pressure, a syrupy substance results,which is a mixture of the free gluconic acid and both its lactones inequilibrium.

We have now found that by controlling the conditions of temperature andtime, it is possible to vary the product resulting from thecrystallization of such a solution. By forming an oversaturated aqueousgluconic acid solution and efiecting crystallization at below 30 C. andpreferably below 25 0., gluconic acid crystallizes out; by efiectingcrystallization of an oversaturated gluconic acid solution at between 30and 70 0., glucono t-lactone crystallizes out; and by efiectingcrystallization of an oversaturated aqueous gluconic acid solution atabove 70 C. glucono "ylactone crystallizes out. It is also possible toconvert these substances into each other by bringing any one of them incontact with water.

However, to obtain any one of these compounds substantially free fromthe other, it is necessary to allow sufiicient time for the desiredconversion at the known rate from the one compound to the other. In nocase should the rate of crystallization exceed the rate of formation ofthe desired compound in aqueous solution at a given temperature andconcentration as, if this rate be exceeded, the other compound may beprecipitated in unchanged form.

Establishment of equilibrium when starting with gluconic acid andforming the t-lactone, or starting with t-lactone and forming gluconicacid, is relatively rapid. On the other hand, establishment ofequilibrium by forming or hydrolizing the v-lactone proceeds relativelyslowly, so that when the -glucono lactone is to be used or formed, theworking conditions must be adjusted to its rate of hydrolysis orformation. In all cases the establishment of equilibrium is hastened bythe higher temperature permissible for the compound sought.

of Acetobact'er, Penicillium and Aspergillus, or the to about to 90%concentration, preferably The rates of hydrolysis of the two lactonesare quite different; the initial speed of reaction with water for theo-lactone being approximately eight times that of the 'y-lactone. A twomolar solution of glucono a-lactone will come to equilibrium in aboutminutes, while a two molar solution of the 'y-glucono lactone willrequire about 120 hours. A very rapid evaporation of the solution at atemperature below 30 will give approximately the initial equilibriummixture of gluconic acid and its lactones. At above 30, a very rapidevaporation will give a mixture of the two lactones. For this reasonmere evaporation to dryness of a gluconic acid solution isunsatisfactory and will not give the'desired results.

Crystallization will be spontaneously efiected by merely allowing thegluconic acid solution to stand at the desired temperature ortemperature range, crystallization probably being effected by chancenucleation from atmospheric dust particles. However, agitation and/orseeding the solu tion with the respective compounds desired, or with anisomorph of the respective compounds desired, and at the predeterminedtemperature or temperature range, facilitates crystallization.

Gluconic acid and its lactones may be crystallized directly from afermentation liquor obtained by fermenting glucose with agluconic acidgenerating micro-organism, such as certain species gluconic acid oreither of its lactones may be transformed into the other by contact withwater I for a suitable length of time, and subsequent crystallization.

' lila'ample I I An oversaturated aqueous gluconic acid solution may beprepared by evaporating at any suitable temperature a gluconic acidfermentation liquor 9U-v by weight of gluconic acid, and preferablyunder sub-atmospheric pressure since at higher temperaturesdiscoloration of the fermentation liquor results. The oversaturated'solution is then concentrated at below 30 C. and preferably at from 20to. 25 C. and crystallization is effected. Agitation and/or seeding withgluconic acid crystals facilitates crystallization. The gluconic acidcrystals are white, substantially free of glucono t-lactone and glucono-lactone, soluble. up to cohol and have a melting point of 117 to'118 C.

' Example II acid by titration and can be reconcentrated to obtain othercrops of crystals.

Example III Example IV Glucono ii-lacton'e is dissolved in water, andpreferably in about one part of water, concentrated as in Example I,with crystallization occurring at between and 110 C., while allowingtime for the glucono -lactone to form. The crystallization of theglucono -lactone should not be effected at a rate in excess of the veryslow formation of the 'y-lactone at the temperature chosen. If this rateis exceeded, the crystallized glucono -lactone will be greatlycontaminated with glucono t-lactone. The amount of glucono t-lactonedecreases with increased temperature and elapsed time.

Many modifications may be made without departing from the spirit andscope of the invention, and we are not to be limited to any specificconcentration of aqueous solution, to any method of efiecting theconcentration or the crystallization of such solution, nor to a solutioncontaining any specific proportions of gluconic acid or its lactones,but claim broadly the crystallization of gluconic acid from anoversaturated aqueous gluconic acid solution at below 30 C., thecrystallization of glucono B-lactone: from an oversaturated aqueousgluconic acid solution at between 30 and 70 C., and the crystallizationof glucono 'y-lactone from an oversaturated aqueous gluconic acidsolution at between '70 and 110 C.

The invention claimed is:

1. The process comprising forming an oversaturated aqueous gluconicacidsolution and effecting crystallization within temperature ranges soselected as to determine the product of crystallization byexcluding-transition temperatures.

2. The process comprising forming an oversaturated aqueous gluconic acidsolution and ef- Iecting crystallization within temperature rangeswholly included between 20 C. and 110 C., and so selected as todetermine the product of crystallization by excluding the two transitionpoints of 30 C. and 70 C.

3. The process comprising forming an oversaturated aqueous gluconic acidsolution. and efabout 40% in cold water, almost insoluble in alfectingcrystallization at below 30 C. to crystallize out gluconic acid.

4. The process comprising forming an oversaturated aqueous gluconic acidsolution, and etfecting crystallization at between 30 and 10 C. tocrystallize out glucono a-lactone.

5. The process comprising forming an oversaturated aqueous gluconic acidsolution, and etfecting crystallization at between 70 and 110 C. tocrystallize out glucono 'y-lactone.

6. The process comprising concentrating an aqueous gluconic acidsolution to oversaturation, and contining the concentration at below 30C. to crystallize out gluconic acid.

'7. The process comprising concentrating an aqueous gluconic acidsolution to oversaturation, and continuing the concentration at between30 and 70 C. to crystallize out glucono a-lactone.

8. The process comprising concentrating an aqueous gluconic acidsolution to oversaturation, and continuing the concentration at between70 and 110 C. to crystallize out glucono 'y-lactone.

9. The process of preparing gluconic acid crystals,,substantially freeof glucono 6-1actone and glucono v-lactone, comprising concentrating anaqueous gluconic acid solution containing in any proportion gluconicacid and both its lactones at below 30 C. to above the satiration pointof gluconic acid;

10. The'process of preparing glucono b-lactone crystals, substantiallyfree of gluconic acid and glucono 'y-lactone, comprising concentratingan aqueous gluconic acid solution containing in any proportion gluconicacid and both its lactones at between 30 and 70 C. to above thesaturation point of glucono a-lactone.

11. The process of preparing glucono -y-lactone crystals containing someglucono a-lactone comprising concentrating an aqueous gluconic acidsolution at between 70 C. and 110 C. to above the saturation point ofglucono -lactone, the amount of glucono 5-lactone decreasing withincreasing temperature and elapsed time.

12. The process of preparing gluconic acid crystals comprisingconcentrating an aqueous 129 gluconic acid fermentation liquor to 55 to90% concentration by Weight of gluconic acid, and continuing theconcentration at between 20 to 30 C. while agitating and seeding withgluconic acid crystals to effect crystallization of gluconic acid.

13. The process of preparing glucono a-lactone crystals comprisingconcentrating an aqueous gluconic acid fermentation liquor to about 90%concentration by weight of gluconic acid at be tween 30 and 70 C., andefiecting crystallization of glucono a-lactone while agitating.

14. The process of converting glucono t-lactone to gluconic acidcomprising dissolving glucono t-lactone in water, concentrating suchsolution" to 55 to 90% concentration by weight of gluconic acid at below30 C. while agitating and seeding with gluconic acid crystals to effectcrystallization of gluconic acid.

15. The process of converting glucono a-lactone to glucono -lactonecomprising dissolving glucono t-lactone in water, concentrating suchsolution to about 85% concentration by weight of gluconic acid, andcontinuing the concentration at between 70 imam 0. while allowing timefor the formation of glucono v-lactone.

16. Process comprising forming an, oversaturated aqueous gluconic acidsolution and isolating a member selected from the group consisting ofgluconic acid, gluconic gamma-lactone and' gluconic delta-lactone bydirect crystallization within temperature ranges so selected as. todetermine the product by excluding transition temperatures, and-removingthe mother liquor:

17. Process comprisingforming an oversaturated aqueous gluconic acidsolution and isolating a member-selected from the group consist-

